Wadia Digital 830 CD player Measurements

Sidebar 3: Measurements

The Wadia's error correction was good—the player produced no glitches in its analog output until track 32 of the Pierre Verany Test CD, which has 1.5mm gaps in the data spiral. Its maximum output level as supplied was 2.25V, with an almost perfect match between the channels. The output impedance was extraordinarily low, at less than 1 ohm (unbalanced), and still just 15 ohms from the balanced outputs. The player's output was absolute-polarity-correct from both sets of outputs, the balanced jacks being wired with pin 2 "hot."

All measurements were taken with the volume control set to its maximum. The frequency response at 0dBFS (fig.1, top pair of traces) showed the expected droop in the top octave, this due to Wadia's DigiMaster filter. It always surprises me that this lack of energy is not as audible as might be expected. This response was identical from both the balanced and unbalanced outputs. The lower two traces in fig.1 show the response with de-emphasis, assessed at -12dBFS. There is a slight excess of mid-treble energy, followed by a greater top-octave rolloff than without de-emphasis. The 830's channel separation (not shown) was superb from either set of outputs, at better than 115dB across most of the audioband, decreasing slightly to 105dB at 20kHz.

Fig.1 Wadia 830, frequency response at 0dBFS (top), and at -12dBFS with de-emphasis (bottom). (Right channel dashed, 0.5dB/vertical div.)

With the player decoding data representing a dithered 1kHz tone at -90dBFS (fig.2), the random noise level in the balanced mode was appropriately low, with no level error. However, AC power-supply components can be seen at 120Hz and 240Hz, which could not be minimized by experimenting with the player's grounding arrangements. The unbalanced outputs had slightly lower levels of these power-supply components than the balanced outputs in the right channel, slightly higher in the left, as can be seen in the wideband spectral plot of the player's output while it decodes data representing a 1 LSB DC offset (fig.3). While this noise is low in absolute terms, its presence was still a surprise in a player of this engineering pedigree.

Fig.2 Wadia 830, spectrum of dithered 1kHz tone at -90dBFS, with noise and spuriae, 16-bit data (right channel dashed).

Fig.3 Wadia 830, spectrum of -1 LSB with noise and spuriae, 16-bit data. (1/3-octave analysis, right channel dashed.)

Wadia Digital
24 Troy Street
River Falls, WI 54022
(715) 426-5900
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